The present invention relates to a microwave transmitter/receiver apparatus applicable to terrestrial communication, satellite communication and other forms of communication. More particularly, the invention relates to a transmitter/receiver apparatus which is small in size and which allows the polarization plane of a polarized wave to be adjusted.
In a microwave communication system having a relatively small capacity, a communication apparatus usually comprises an antenna, a primary radiator, a transmit/receive multiplexer, a transmitter, a receiver, and other units. The transmitter and the receiver, which are discrete units, are connected to the transmit/receive multiplexer by a waveguide. The multiplexer, in turn, is connected to the primary radiator, or horn, by a feeder waveguide. The transmitter and the receiver are sometimes accommodated in a single housing.
In such a construction, the prerequisite is that the polarization plane of a polarized wave be aligned with the polarization plane of the horn in order to increase the signal-to-noise (SN) ratio of transmit and receive signals. One approach for fulfilling this requirement which is known in the art is to make the horn, transmit/receive multiplexer, transmitter, receiver and feeder waveguide rotatable. As discussed later in detail, the problem with this approach is that a polarization adjusting mechanism becomes complicated and expensive. Since the loss of the feeder waveguide is increased, the transmit output has to be made greater thereby increasing both the power consumption and the dimensions of the apparatus.
Another prior art approach is inserting a polarizer between the transmit/receive multiplexer and the horn. The polarizer scheme, however, adds to the cost due to the use of a polarizer and brings about a feed loss due to the use of the feeder waveguide. The feed loss of the waveguide invites the same disadvantages that occurs in th first-mentioned approach. Further, since both of these prior art approaches interconnect the circuits using a feeder waveguide, they cannot be implemented without increasing the overall apparatus scale and furnishing each junction with an air- and liquid-tight structure. These prior art approaches result in prohibitively long assembling and adjusting time.